Coating method and products obtained by same

ABSTRACT

The invention concerns a method for producing high resolution patterns on a support comprising the following steps: high resolution printing of a varnish on the support; treating the support by electrolysis; washing and drying the support.

CROSS REFERENCE TO RELATED APPLICATION

The present application is the U.S. national stage application ofInternational Application PCT/EP00/06143, filed Jun. 30, 2000, whichinternational application was published on Jan. 11, 2001 asInternational Publication WO 01-2186 in the French language. TheInternational Application claims priority of Luxembourg PatentApplication 90412, filed Jul. 2, 1999.

PRIOR ART

Numerous packaging material coating processes are known, the followingbeing a non-exhaustive list:

aqueous coating in which the liquid to be coated is a suspension orsolution of an agent in water;

solvent coating in which the liquid to be coated is a suspension orsolution of an agent in one or more solvents;

hot-melt coating in which the liquid to be coated is obtained byadjusting the agent to be deposited to a temperature which makes itliquid;

solvent-free coating in which the agents to be deposited are in liquidform (monomers) and will cure and polymerise by catalysis;

coating by evaporation of a solid which sublimes under vacuum onto thesupport;

lamination coating in which the coating is a film which is attached tothe support with an adhesive;

transfer coating in which the agent to be deposited is alreadyprovisionally attached to a film to which it adheres poorly in order tobe removed from the provisional support and finally attached to thefinal support by some known means.

The coating provided by these processes is generally complete, sometimespartial, but none of these coating methods allows the production of highresolution patterns.

U.S. Pat. No. 5,721,007 describes a process in which a support is coatedwith a metallic layer; an electrically insulating lacquer is printed athigh resolution onto a first part of the coated support; one or moremetallic layers are deposited onto a second part of said support, i.e.the part of the support not covered by the lacquer, by electrolysis inorder to form the conductive tracks of the circuit; the electricallyinsulating mask is then removed in order to allow engraving of thesupport coating not covered by said metallic layer or layers depositedonto said support between the lacquer. This method is used, for example,in the production of electrical circuits, in particular for theproduction of flat cables. Although this method allows high resolutionprinting, it does not permit deposition of metal onto the lacquer.

OBJECT OF THE INVENTION

The object of the present invention is accordingly to provide a processfor the production of a multilayer substrate having high resolutionpatterns and permitting deposition of metal onto the lacquer.

GENERAL DESCRIPTION OF THE CLAIMED INVENTION AND THE PRINCIPALADVANTAGES THEREOF

This object is achieved according to the invention by a process allowingthe production of high resolution patterns and comprising the followingsteps:

high resolution printing of a lacquer on the coated support;

treatment of the support by electrolysis;

washing and drying of the support.

According to an important feature of the invention, the lacquer is acharged lacquer. Said charged lacquer not only allows specific areas onthe support to be protected, but also allows subsequent deposition ofmetal onto said charged lacquer.

High resolution printing of a lacquer onto a support allows the creationof fine and high resolution patterns on this support. This process isindependent of the support and the support coating process. This processmay, in principle, be applied to any support.

Before printing, the support may be coated with a layer which preferablycomprises metal.

Said charged lacquer which may for example comprise conductive materialsand/or materials acting as a barrier to or filtering electromagneticwaves.

The material acting as a barrier to or filtering electromagnetic wavespreferably absorbs and/or reflects at least part of the electromagneticwaves.

Treatment of the coated support by electrolysis advantageously compriseselectrolytic engraving of the coating on the unprinted part of thecoated support.

According to one specific embodiment, said support is subjected toelectrolytic deposition on the conductive printed part after washing anddrying.

Treatment of said support by electrolysis comprises electrolyticdeposition of one or more metals or the alloys thereof onto the printedpart of the support.

The lacquer is preferably printed onto said support by photogravure.Photogravure is advantageously performed by a photogravure unitcomprising at least one cylinder having printing zones consisting ofengraved cells, the outermost cells of each pattern being interconnectedto ensure linear continuity of the outlines. The cylinder cells arepreferably arranged at a screen ruling of 175 to 700 cells per inch (per2.5 cm), preferably of 350 cells per inch (per 2.5 cm). The cells of theoutlines are preferably interconnected to achieve continuity of thegraphical element and avoid any stepped appearance. Said photogravureunit is capable of printing a coating with very fine patterns of between150 and 25 μm, preferably of 50 μm.

Engraving is preferably performed by electrolysis between the metalliccoating of the support to be treated and an anode immersed in an aqueouselectrolyte. Said anode is preferably a titanium anode consisting offolded sheet. Said aqueous electrolyte advantageously comprises aninorganic acid and the salt thereof or an inorganic base and the saltthereof, preferably NaOH+NaCl at a concentration of 10%. Once thelacquer has been applied onto the coated support, the electrolytictreatment of the support allows the removal of the coating from saidsupport at those points where the lacquer was not applied. In thismanner, a support comprising high resolution patterns is obtained. Theelectrolyte is selected such that the products released into the aqueousphase by electrolysis attack the metallic coating with a mixture of theacidic type and the salts thereof or alternatively with an alkali andthe halogen salts thereof. Depending upon the electrolyte selected andthe density of the printed pattern, products are obtained which havedifferent characteristics with regard to reflection, transmission andabsorption of incident electromagnetic radiation. Reflection andtransmission rates may preferably range between 0 and 100%, while theabsorption rate may range from 0 to 50%.

Electrolytic deposition is preferably performed by electrolysis of oneor more metals and/or the alloy thereof, by dissolution of a solubleelectrode containing at least the electrode metal or metals. Themetallic deposit or successive metallic deposits allow(s) the creationof patterns with high resolution and high precision on a support.

The products of the process described above may have useful properties,especially for applications in the field of electromagnetic waves, inparticular in the field of microwaves.

The process allows the production of multilayer products having veryparticular properties with regard to the reflection, transmission andabsorption of incident electromagnetic radiation. Depending upon theparticular case, incident electromagnetic radiation on the product maybetransmitted at a rate of 0 to 100%, reflected at a rate of 0 to 100%and/or absorbed at a rate of 0 to 50%. Such products have many andvaried applications; they may be used, for example, as a filter forelectromagnetic radiation, said filters being transparent to visiblelight. A heat-resistant polymeric film, for example of polyester, may becoated with a layer which heats up when the incident electromagneticenergy is partially absorbed by the coating. Said coating may bemetallic with a resistivity of between 0.0005 and 0.1 ohm/square,preferably of 0.01 ohm/square, for example of aluminium with a thicknessof between 0.001 and 1 μm. Under these conditions, the product isvisually highly transparent and heats up to elevated temperatures (ofthe order of 200 to 300° C.) when struck by electromagnetic radiationand in particular by microwaves. The calorific energy may amount to upto 50% of the incident energy.

The quantity of energy which is absorbed, transmitted or reflectedvaries as a function of the dimensions and distribution of the coatingapplied to the film. Below a predetermined threshold, the transmittedenergy is greater than the reflected energy; beyond this threshold,transmitted energy is less than the reflected energy.

By filling the lacquer with agents which enhance the electromagneticwave absorption effect, it is possible to create products which areopaque to electromagnetic waves. In this way, it is for example possibleto create film which is opaque to microwaves which could be applied tothe window of a microwave oven door. By providing a grid with thin linesat a spacing of half the wavelength of the microwaves, a microwavebarrier film is obtained which is almost completely transparent tovisible light waves. Said film may be applied onto a microwave ovendoor, through which the interior of the microwave oven may readily beobserved in complete safety.

The process also allows the creation of multilayer products. A secondmetallic deposit may be deposited onto a first metallic deposit bypassing the support again through the printing station and the treatmentstation. Of course, the number of times the support passes through theprinting and treatment stations and, consequently, the number ofmetallic deposits, is not limited to two.

Depending upon the nature of the coating and the filler in the appliedlacquers, it is possible to create products, the composition of which isdetermined by the desired electromagnetic energy conversions. It is alsopossible to create barriers to electromagnetic radiation of certainwavelengths. Both options may optionally be combined to provide productswhich, as a function of wavelength, are both absorbent and reflective.

It is thus possible to create a package which reflects microwaves in onepart of the package and absorbs part of the microwaves in another part.This makes it possible to use a microwave oven to heat foods which areto be adjusted to different temperatures.

The present invention also provides a multilayer product comprising thefollowing layers:

base support made from a material transparent to visible light and toelectromagnetic waves,

at least one high resolution metallic coating covering less than 5% ofthe area of the support,

at least one layer of lacquer covering the metallic coating,

in which the coating is arranged on the support in a pattern invisibleto the naked eye, filtering a specific range of electromagnetic waves.

For the purposes of the present document, the term “filtering” meansthat between 0 and 99.9% and preferably between 0 and 95% of theincident waves pass through the product. The product may thus bevirtually transparent or opaque to a specific range of electromagneticwavelengths.

For the purposes of the present document, the term “transparent tovisible light” means that between 80 and 99.9% and preferably between 90and 95% of visible light pass through the product.

According to an advantageous embodiment, the product comprises anadditional metallic coating layer which covers at least part of thelacquer layer.

According to another embodiment, the invention relates to a multilayerproduct comprising the following layers:

base support made from a material transparent to visible light and toelectromagnetic waves,

high resolution lacquer covering at least 5% of the area of the support,

at least one metallic coating covering the lacquer and filtering aspecific range of electromagnetic waves,

in product the lacquer is arranged on the support in a pattern invisibleto the naked eye.

An additional lacquer layer may, at least in part, cover the metalliccoating which may in turn be covered, at least in part, by an additionalcoating layer.

The base support is generally a film of a synthetic material, such asfor example a polyester film. However, any other material may besuitable provided that it is transparent to visible light and to theselected range of electromagnetic waves. It is moreover necessary for itto be possible to cover such a material with a high resolution patterncomprising a coating and/or a lacquer.

The proposed product generally absorbs between 0 and 95% of the specificrange of incident electromagnetic waves, reflects between 0 and 100%and/or transmits between 0 and 100% of the non-absorbed waves as afunction of the pattern, the nature and quantity of the coating.

According to a particular embodiment, the product absorbs from 0 to 50%of the energy of the electromagnetic waves and reflects and/or transmitsthe non-absorbed energy.

The product thus comprises a filter for a range of electromagnetic wavesand transparent to visible light; it may even comprise a filter which isopaque to electromagnetic waves and transparent to visible light.

In particular, the electromagnetic waves are, for example, microwavesand the product may consequently be used as packaging for microwaveableproducts, i.e. for packaging foodstuffs which may be reheated in amicrowave oven.

DESCRIPTION ASSISTED BY FIGURES

Further peculiarities and features of the invention will emerge from thedetailed description of several advantageous embodiments shown below byway of illustration with reference to the attached drawings, which show:

FIG. 1: a cross-section through a film at various stages (A, B and C) ofproduction (uncoated support, lacquer with filler, electrolytic deposit)

FIG. 2: a cross-section of another film at various stages (A, B and C)of production (coated support, lacquer, engraving)

FIG. 3: a cross-section of yet another film at various stages (A, B, Cand D) of production (coated support, lacquer with filler, engraving anddeposit)

FIG. 4: shrinkable sleeve

FIG. 5: transparent film filter

FIG. 6: microwave oven door

FIG. 7: microwaveable packaging for coffee topped with whipped cream

FIG. 8: microwaveable meal tray

FIG. 9: overall diagram of a machine for performing the process

FIG. 10: detail of printing unit

FIG. 11: schematic diagram of printing unit

FIG. 12a: desired shape of an impression

FIG. 12b: photogravure window (engraved zone with continuity line incontact with engraved cells)

FIG. 12c: photogravure window (engraved zone with continuity line not incontact with engraved cells)

FIG. 12d: printed result

FIG. 13: schematic of physico-chemical treatment unit for film.

In the Figures, the same references denote identical or similarelements.

FIG. 1A shows a cross-section through a support film 10 on which (inFIG. 1B) is printed a discontinuous layer 20 of charged lacquer. FIG. 1Cshows a metallic layer 30 deposited by electrolysis on the printed layer20 of the film 10. It is thus possible to deposit a metallic layer 30with a high resolution pattern onto a virgin film, i.e. onto a filmwithout a continuous metallic coating. In this manner, it is possible toobtain films with high resolution metallic patterns on a film 10.

FIG. 2A shows a film 10 comprising a metallic coating 15. A protectivelacquer 20 is printed (FIG. 2B) onto the coating layer and the part ofsaid metallic coating which is not covered by the protective lacquer isremoved (FIG. 2C) by electrolysis.

FIG. 3A shows a film 10 comprising a metallic coating 15. A protectivelacquer 20 is printed (FIG. 3B) onto the coating layer and the part ofthe metallic coating which is not covered by the protective lacquer isremoved (FIG. 3C) by electrolysis. After washing and drying, a metalliclayer 30 is deposited on the protective lacquer layer. It is thuspossible to manufacture multilayer materials.

It is, for example, possible to produce a heat-shrinkable sleeveconsisting of a heat-shrinkable film. It may be intended for holding twotins together. Particular attention should be paid to the shrink zoneswhich are in contact with the tins and will be provided with zonesreactive towards microwaves. The parts of said sleeve not in contactwith the tins will not undergo any heating in the microwave over andwill thus not shrink, while selective heating will cause shrinkage ofthe perimeter of said sleeve, clamping the two tins together, forexample to make them into a promotional offer.

FIG. 5 shows a heat-resistant polymeric film, preferably of polyester,coated with a layer which heats up when the incident electromagneticenergy is partially absorbed by the coating, which may be metallic, witha conductivity between 1 and 2,000 ohm/square, preferably 100ohm/square, for example consisting of a layer of aluminium obtained byvacuum sublimation of a thickness of 10 to 10,000 Angström, preferablyof an optical density of 0.6. Under these conditions, the packagingmaterial is very highly visually transparent and heats up to 280° C.when electromagnetic radiation of a frequency of 2,450 MHz strikes it;the resultant calorific energy may amount to up to 50% of the incidentenergy.

By varying the dimensions of the coating, the quantity of energyabsorbed, reflected and transmitted will be modified.

Below a threshold, the transmitted energy is greater than the reflectedenergy. Beyond this same threshold, reflected energy is greater thanthat transmitted.

Another exemplary embodiment is shown in FIG. 6 in which a film isapplied against a microwave oven door.

By coating a film which is transparent to visible light with aprotective lacquer comprising agents which enhance the absorptive and/orreflective properties of a film, it is possible to produce materialswhich are opaque to certain electromagnetic radiation while stillremaining transparent to visible light. Said material comprises acoating of aluminium obtained by vacuum sublimation, of a thickness ofat least 600 Angström covered with a lacquer filled with particles whichenable an overall conductivity of between 1 and 10 ohm/square,preferably of 2.5 ohm/square, to be achieved. Said particles arepreferably aluminium elements of small dimensions (5 to 15 μm,preferably 10 μm) obtained by vacuum deposition. The wavelength ofdomestic microwave ovens is 12.5 cm. The process according to theinvention permits the production of 50 μm lines. Thus, with lines ofaluminium approx. 10 μm thick, 50 μm wide and at half wavelengthspacing, i.e. every 6.5 cm, a grid is obtained (FIG. 10) which is opaqueto microwaves. The surface occupied by this grid is(50×65000×2)/(65000)²=0.15% and it will be 99.85% transparent to visiblelight. A film which is almost completely transparent to visible lightbut is nevertheless opaque to microwaves is thus obtained. Said film maybe applied against a microwave oven door. The door window is transparentto visible light and it is thus possible to observe what is happeninginside the oven, but the microwaves are not transmitted through thedoor.

FIG. 7 shows a cover for a beverage of the type “coffee topped withwhipped cream” which may be arranged over a vessel containing coffee inits lower part and cream floating on the coffee in its upper part beforethe beverage is heated in a microwave oven.

Before drinking the coffee topped with whipped cream, the consumer willplace the vessel with its cover in a microwave oven to heat it.

The cover is arranged on the vessel and the upper part of the cover,which surrounds the cream, reflects microwave radiation while the lowerpart, which surrounds the coffee, absorbs some of the microwaveradiation. As a result, said cream remains cold, while the heatgenerated by absorption of the microwave radiation in the lower part istransmitted to said coffee, so heating it. By using such a cover, abeverage is obtained with hot coffee and lukewarm, smooth cream.

Another example of use of a material according to the present inventionis a meal tray, PR, for foods to be heated to different temperatures(FIG. 8).

Such a tray comprises a complete meal, for example with the followingcontents in its compartments:

a) a starter: asparagus with vinaigrette dressing

b) a main course: fish in a sauce

c) a dessert: ice cream.

The starter (a) must be eaten lukewarm, the main course (b) hot and theice cream (c) cold. These three types of food will be arranged on athermoformed meal tray, PR, which is sealed by a lid (not shown) to formenclosures which communicate with the exterior only by means of vents(not shown). Around the compartment (a) for the starter, a film isarranged on the walls formed by the tray and the lid to create anenclosure (a) with a metallic coating of a conductivity of 0.1Mohm/square; enclosure (b) around the fish will have no coating andenclosure (c) will be coated with a multilayer film which will beequivalent to that providing a barrier to microwave radiation (FIG. 6),such that the ice cream is not heated. Placing the tray, PR, in amicrowave oven for 90 s results in the asparagus in compartment (a)being at 25° C., the fish in compartment (b) at 35° C. and the ice creamin compartment (c) at 0° C., starting from a tray, PR, straight from thedeep-freeze.

Depending upon the nature of the energy conversion layer comprising thecoating of the printed lacquer or lacquers optionally containing afiller, the electrolytic deposit or deposits and the electrolyticengraving or engravings, it is possible to produce materials, thecomposition of which will be determined by the desired electromagneticenergy conversions and even to produce barriers to electromagneticradiation for certain wavelengths and, optionally, to combine bothoptions in order to provide products which, as a function of wavelength,are both absorbent and reflective.

FIG. 9 shows an installation for performing the process described above.This installation comprises a feed station A which accommodates the filmprovided with its base layer BA1 wound on a reel. In said feed station,the reel is unwound to supply a heliogravure printing station B; then,on leaving said photogravure printing station, the strip BA2 passes intoan electrolysis station C which performs the physico-chemical treatmentof the windows of the film BA3. Downstream from this electrolysisstation C is a washing station D in which the water-soluble lacquer isoptionally removed to yield the film BA4 and the strip is rinsed. Saidstrip BA4 then passes into a drying station E and, finally, into aninspection station F before arriving at the winder G.

The feed station A comprises an unwinder A1 which holds the reel A2.This unwinder is driven by a motor controlled by a delivery unit A3,which maintains a specified tension in the strip BA1. The strip thenpasses into the printing station B which comprises a printing unit(FIGS. 10 and 11) with an ink fountain B1, a photogravure cylinder B2immersed in the ink fountain B1 to cover the surface provided withphotogravure cells and the outline of the window. This cylinderinteracts with a doctor blade B3 which removes the ink from the surfaceto leave behind only the ink inside the cells or the engraving. The inkfountain B1 is supplied by means of a pump B5 and a line B6 from areservoir B4 containing the coating agent. Said reservoir B4 is providedwith a viscosity detection means B6, such as a viscosimeter, so that theviscosity of the coating liquid may be controlled.

The photogravure unit B may be equipped with a spot reading system, or amarker detectable by a photoelectric cell, arranged on the metallisedstrip which will allow the strip to be guided, such that the position ofthe printing window is in register with the patterns on the metallisedstrip comprising optionally preprinted graphic elements.

The level of liquid in the ink fountain B1 is controlled by an overflowB7 with a return line to the reservoir B4, such that the photogravurecylinder B2 is always immersed to the same depth in the ink fountain B1.

The cylinder B2 interacts with a presser roller B10 located above saidstrip BA1, cylinder B2 being located below the strip.

Said strip BA1 is composed schematically, as shown in FIG. 3 , of asupport 10 of a plastics material and a base coating 15, such as ametal.

While turning in the direction of the arrows, the photogravure cylinderB2, with the presser B10, compresses said strip BA1 and leaves lacquerimpressions corresponding to the printing windows or zones or coatings,I, corresponding to the windows.

FIG. 11 is a top view of the printing unit shown in FIG. 10. This Figureshows the photogravure cylinder B2, the presser roller B10 with an arrowindicating the compression, together with the strip BA from above. Thephotogravure cylinder B2 has a surface engraved in accordance with aphotogravure window or printing zone B21 of a relatively complicatedshape which creates the impression I of the lacquer on the under surface15 of said strip BA1 (which then becomes strip BA2).

FIGS. 12A-12D show the production of the engraved surface of thephotogravure window in greater detail.

FIG. 12A shows the desired outline of the photogravure window, i.e. theoutline of the future graphic element (I100).

On the basis of this shape I100, the surface of the photogravure windowis engraved into the cylinder. This window consists of an engravedsurface comprising reservoirs or cells K100, separated by low wallsK101, the whole being surrounded by a rule K102, which adjoins thereservoirs and the gaps between the reservoirs K100.

In this Figure, the cells are represented by black squares with roundedcorners, said squares being optionally truncated and separated by blanklow walls (partitions, also known as bridges), K101.

All these cells or reservoirs are in this case surrounded by a rule,i.e. a very narrow notch which fills up with ink but limits spreading ofthe ink from the cells in order to give the printed image a continuous,precise outline, so defining the limit of the window in a precise andpredetermined manner.

In FIG. 12B, this rule K102 passes contiguously over the reservoirs oradjacently thereto.

In the case of FIG. 12C, the window 1200 also comprises cells K200separated by low walls K201, the whole being surrounded by a rule K202which is further from the edge of said cells K200 (whether truncated ornot) than in the embodiment in FIG. 12B.

The fineness of the line constituting the rule depends upon theresolution of the plotter which drew the window or windows; thus, thetypes of engraving shown in FIGS. 12B and 12C are selected on the basisof the viscosity of the liquid used for printing. As stated, once dried,this liquid is a passivity agent, i.e. is inert with regard to thephysico-chemical action to be performed.

Finally, FIG. 12D shows the printed image 1300 with its very precise,unstepped outline.

To return to FIG. 9, the electrolysis station C comprises anelectrolysis tank C1 which is skimmed by the strip BA2, which has beenprinted in the printing station B. Said electrolysis station alsocomprises an extractor hood C2 for the electrolysis gases. Station C2 isshown in detail in FIG. 13.

The electrolysis tank C1 is equipped with an overflow to discharge thesurplus electrolyte C9 in such a manner as to maintain a constant levelof electrolyte C9. Said electrolyte is discharged into a funnel C15which leads to a pump C8 which in turn returns the electrolyte to theelectrolysis tank C1. At the outlet, there is a collection funnel C15which collects the liquid dripping from the strip BA3 which has beenwrung out by passing between two rollers C16, C17. The wrung out liquidis collected in the funnel C15 and returned to the reservoir C9.

The electrolysis tank may be used either to engrave the film BA2 or toprovide a metallic deposit on said film BA2.

When the tank is used for engraving, the printed film BA2 is negativelypolarised and skims an electrolyte C9 at a distance of a few millimetersfrom the tips of a titanium type metallic anode C20 which is insolubleduring electrolysis and is negatively polarised. The shape of the anodeis obtained by folding a metal sheet. A PVC insulator C22 is arrangedbetween each point of said anode C20. Said electrolyte C9 is selectedsuch that the products released into the aqueous phase by electrolysisattack the metallic coating 15, but not the impression I. Saidelectrolyte C9 attacks the metal with a mixture of the acidic type andthe salts thereof or alternatively of the basic type and the saltsthereof. NaOH+NaCl are preferably used in proportions by weight of 10%relative to the weight of water. The conditions under which electrolysisis performed depend upon the nature of the metal to be electrolysed.Said electrolyte C9 removes the metallic coating 15 from the film B2 inthose areas not protected by the impression I.

When the tank is used to provide a deposit, the printed film BA2 ispositively polarised and skims an electrolyte C9 at a distance of a fewmillimeters from the tips of a metallic anode C20 which is solubleduring electrolysis and is negatively polarised. The shape of the anodeis obtained by folding a metal sheet. A PVC insulator C22 is arrangedbetween each point of said anode C20. An electrode of copper and anaqueous electrolyte consisting of 220 g/l of CuSO₄ and 20 g/l of H₂SO₄will preferably be selected to provide a copper deposit. The currentapplied will advantageously be 10 A/dm².

Finally, the window printing and electrolysis operations may be repeatedwith different shaped windows one on top of the other, for example tocreate an integrated circuit, in which case there will be a successionof alternating stations B, C and optionally D.

The film BA3 then passes into the washing station D. This washingstation rinses the strip BA3 to remove any electrolyte residues and todissolve the coating layer, in particular the passivity layer. Thiswashing station D consists of various return rollers D1, D2 conveyingsaid strip BA3 into a first tank D4 and then into a second tank D5.These tanks contain an electrolyte rinsing liquid and/or a coatingsolvent. The detailed structure of these washing tanks will not bedescribed. The system comprises a set of rollers which define aconveying route for the strip through the washing bath.

Washing is performed by wringing out between steel rollers and polymerrollers in order to limit drive and to facilitate evaporative drying ofthe washing liquid, such that the film is dry and comprises no traces ofelectrolyte which are incompatible with its subsequent use.

Downstream from the washing station D, the strip BA4 passes into thedrying station E equipped with air ventilation and extraction means E1,E2, E3, E4 and, finally, the dried strip BA5 passes into an inspectionstation F equipped with a video camera F1 which views an area of thefilm BA5 to monitor production quality. This inspection is complementedby a measurement of optical density and resistivity (not shown). Theseinspection measures are carried out continuously. At the outlet from theinspection station F, the film is wound in a winding station G. Saidwinding station is of a similar construction to the unwinder A, butoperates in the reverse direction. It comprises a support G1 fitted witha motor and forming the reel G2.

After inspection of the strip, the strip is fed in and wound onto a reelunder controlled tension such that it is not deformed by the extra-thickareas.

The strip is guided through the installation of FIG. 9 in a synchronisedmanner by means of register marks and sensors together with controlcircuits, none of which are shown.

The installation has the advantage of a treatment speed which may exceeda treatment speed of 250 m/min. Treatment is unaffected by the presenceof metallic oxides which protect the metallised side of the film, whichis a particular advantage in comparison with the prior chemical process.The possibility of depositing a metallic layer of a different nature tothat which has been corroded makes it possible to produce metallicmultilayers.

The resolution of the metallised line is the same as the printingresolution because the thickness of the corrosion mask may be 2 micronsor less.

Finally, with regard to convenience of production, printing of thecorrosion resist may be performed on a machine which is independent ofthe treatment machine.

The process and installation described allow the production of a filmcomprising multiple layers of insulating and conductive materials,insulating and metallic materials capable of being used when printingmaterials.

Depending upon the nature of the energy conversion layer comprising thecoating of the printed lacquer or lacquers optionally containing afiller, the electrolytic deposit or deposits and the electrolyticengraving or engravings, it is possible to produce materials, thecomposition of which will be determined by the desired electromagneticenergy conversions and even to produce barriers to electromagneticradiation for certain wavelengths and, optionally, to combine bothoptions in order to provide products which, as a function of wavelength,are both absorbent and reflective.

EXAMPLE

Electromagnetic waves penetrate as a function of frequency. The higheris the frequency, the greater the penetration of the wave.

In absorbent materials, when an incident wave is stopped, its energy isabsorbed.

In reflective materials, the incident wave does not penetrate and isreflected. The incident energy is equal to the reflected energy.

In transparent materials, the energy of the incident wave which passesthrough unobstructed, without reflection and without absorption is equalto the transmitted energy.

Depending upon the nature of the material and the wave, the normalsituation is for all three phenomena to occur; complete reflection andcomplete transmission are the two extremes.

In the case of microwaves, as a function of the thickness of thealuminium, it has been found that a layer thickness of 1 micron causesreflection of the incident wave, with neither absorption nortransmission. A layer of aluminium 1 micron in thickness is said to beopaque to microwaves.

In the thickness range from 10 Å (angstrom) to 600 Å of aluminium, partof the incident energy is reflected, part is transmitted and the balanceabsorbed and converted into heat.

Thick layers promote reflection, while thin layers promote transmission.

Absorbed energy is at its maximum for aluminium layer thicknesses of theorder of 50 Å.

A coating, which will be the function of the aim to be achieved will bedeposited on a support of the polyester type. Removal of the coatingwill cancel the effect. The effect of the coating will be enhanced byincreasing the lacquer filler and still further enhanced by providing anelectrolytic deposit.

Polyester is coated with a layer of aluminium of resistivity 0.001ohm/square by vacuum sublimation. A skin temperature on the polyesterfilm of 200° C. may be achieved (30% of incident energy is absorbed).

Part of the film is demetallised. In this demetallised zone, themicrowave energy will no longer be absorbed; since the polyester istransparent to microwaves, all the microwave energy will be transmitted(no reflected energy). Said polyester is said to be transparent tomicrowaves.

A lacquer containing an aluminium filler of a conductivity of 0.0005ohm/square is printed onto the same coated film. A material of aconductivity of 0.0015 ohm/square is obtained. A material which canreach a skin temperature of 280° C. is obtained.

A complementary 400 Å metallic deposit is provided. The material thenbecomes reflective to microwaves. Transmitted energy approaches 0 andthe material is opaque to microwaves.

The nature of the coating, the fillers and the electrolytic deposit ordeposits is selected as a function of the nature of the incident waves(frequency) and the desired effect (reflection, transmission andabsorption).

In the same manner, lead may also be used as a barrier to X rays.

What is claimed is:
 1. A multilayer product comprising the followinglayers: a base support made from a material transparent to visible lightand to electromagnetic waves, at least one metallic coating coveringless than 5% of the area of the support, said metallic coating beingapplied at a resolution between 25 and 150 μM, at least one layer oflacquer covering the metallic coating, wherein the coating is arrangedon the support in a pattern invisible to the naked eye, and filters aspecific range of electromagnetic waves.
 2. A product according to claim1, wherein an additional metallic coating covers the lacquer.
 3. Aproduct according to claim 1, wherein the base support is a polyesterfilm.
 4. A product according to claim 1, wherein the product absorbsbetween 0 and 95% of the incident waves, and reflects between 0 and 100%and/or transmits between 0 and 100% of the non-absorbed waves as afunction of the pattern and the nature and quantity of the coating.
 5. Aproduct according to claim 4, wherein the product absorbs from 0 to 50%of electromagnetic wave energy and reflects and/or transmits thenon-absorbed energy.
 6. A product according to claim 1, wherein theproduct comprises a filter for electromagnetic waves and is transparentto visible light.
 7. A product according to claim 1, wherein the productcomprises a filter which is opaque to electromagnetic waves and istransparent to visible light.
 8. A product according to claim 1, whereinthe base support is transparent to microwaves.
 9. A product according toclaim 1, comprising packaging for microwaveable products.
 10. Amultilayer product comprising the following layers: a base support madefrom a material transparent to visible light and to electromagneticwaves, a lacquer covering less then 5% of the area of tie support, saidlacquer being applied at a resolution between 25 and 150 μm, at leastone metallic coating covering the lacquer and filtering a specific rangeof electromagnetic waves, wherein the lacquer is arranged on the supportin a pattern invisible to the naked eye.
 11. A product according toclaim 10, wherein an additional layer of lacquer covers the metalliccoating at least in part.
 12. A product according to claim 11, whereinan additional metallic layer covers the additional layer of lacquer. 13.A product according to claim 10, wherein the base support is a polyesterfilm.
 14. A product according to claim 10, wherein the product absorbsbetween 0 and 95% of the incident waves, and reflects between 0 and 100%and/or transmits between 0 and 100% of the non-absorbed waves as afunction of the pattern and the nature and quantity of the coating. 15.A product according to claim 10, wherein the product comprises a filterfor electromagnetic waves and is transparent to visible light.
 16. Aproduct according to claim 10, wherein the product comprises a filterwhich is opaque to electromagnetic waves and is transparent to visiblelight.
 17. A product according to claim 10, wherein the base support istransparent to microwaves.
 18. A product according to claim 10,comprising packaging for microwaveable products.
 19. A process forproducing a product having high resolution patterns on a supportcomprising the following steps: printing the support with a lacquerapplied at a resolution between 25 and 150 micrometers; coating thelacquer with a metallic coating; treating the product by electrolysis;and washing and drying the product; the lacquer covering less than 5% ofthe area of the support and the metallic coating comprising a metal ormetals, one or more oxides, or one or more metal or metalloid salts. 20.A process according to claim 19 further comprising the step of printingthe metallic coating with an additional layer of lacquer, wherein theadditional layer of lacquer covers the metallic coating at least inpart.
 21. A process according to claim 20 further comprising the step ofcoating the additional layer of lacquer with an additional layer ofmetallic coating.
 22. A process according to claim 20 wherein thelacquer is arranged on the support in a pattern invisible to the nakedeye.
 23. A process according to claim 19 wherein the lacquer is printedonto the support by photogravure.
 24. A process according to claim 23wherein photogravure is performed by one or more photogravure units,said photogravure units comprising at least one cylinder having printingzones consisting of engraved cells, wherein outermost cells of eachprinting zone are interconnected to ensure linear continuity of printingzone outlines.
 25. A process according to claim 19 wherein the step oftreating the support by electrolysis comprises electrolytic engraving ofthe coating on a portion of the support not printed with the lacquer.26. A process according to claim 25, wherein the step of treating thesupport by electrolysis comprises electrolytic deposition on a printedportion of the support after the step of washing and drying.
 27. Aprocess according to claim 25, wherein said electrolytic engraving isperformed by immersing the support and an anode in an aqueouselectrolyte and passing a current therethrough.
 28. A process accordingto claim 27, wherein the anode is a titanium anode in the form of afolded titanium sheet.
 29. A process according to claim 27, wherein theaqueous electrolyte comprising an inorganic acid and its salt or aninorganic base and its salt, preferably NaOH+NaCl at a concentration of10% by weight.
 30. A process for producing a product having highresolution patterns on a support comprising the following steps: coatingthe support with a metallic coating applied at a resolution between 25and 150 micrometers; printing the metallic coating with a layer oflacquer, treating the product by electrolysis; washing and drying theproduct; the metallic coating covering less than 5% of the area of thesupport and comprising a metal or metals, one or more oxides, or one ormore metal or metalloid salts.
 31. A process according to claim 30,further comprising the step of coating the lacquer with an additionallayer of metallic coating, wherein the additional layer of metalliccoating covers the lacquer at least in part.
 32. A process according toclaim 30, wherein the lacquer is printed onto the support byphotogravure.
 33. A process according to claim 32 wherein photogravureis performed by one or more photogravure units, said photogravure unitscomprising at least one cylinder having printing zones consisting ofengraved cells, wherein outermost cells of each printing zone areinterconnected to ensure linear continuity of printing zone outlines.34. A process according to claim 30, wherein the step of treating thesupport by electrolysis comprises electrolytic engraving of the coatingon a portion of the support not printed with the lacquer.
 35. A processaccording to claim 34, wherein the step of treating the support byelectrolysis comprises electrolytic deposition on a portion of thesupport after the step of washing and drying.
 36. A process according toclaim 34, wherein said electrolytic engraving is performed by immersingthe support and an anode in an aqueous electrolyte and passing a currenttherethrough.
 37. A process according to claim 36, wherein the anode isa titanium anode in the form of a folded titanium sheet.
 38. A processaccording to claim 37, wherein the aqueous electrolyte comprises aninorganic acid and its salt or an inorganic base and its salt,preferably NaOH+NaCl at a concentration of 10% by weight.